Intercepting-trunk system



April 10, 1928.

' M. SCHWARTZ INTERCEPTING TRUNK SYSTEM Original Filed Feb. 9. 1924 2 Sheets-Sheet 1 WWW April 10, 1928.

' M. SCHWARTZ mmncsrwme TRUNK SYSTEM ri inal Filed Feb.9. 1924 2 Sheets-Sheet 2 .0 INN e 5v mg Q Mg Patented Apr. 10, 1928.

UNITED STATES-PATENT OFFICE.

MICHAEL SCHWARTZ, OF CHICAGO, ILL INors, Assi'enon, BY iunsun ASSIGNMENTS, To AUTOMATIC ELECTRIC Inc, OF CHICAGO, ILLINOIS, A CORPORATION OE DELA- WARE.

' i t1 INTERGEPTING-TRUNK sYsTEM. h g1 5 u k, W

Application filed February 9, 1924, Serial No. 691,679. Renewed August 26, 1927.

The present invention relates in general to telephone systems, but is particularly concerned with the provision of new and improved trunking arrangements for handling calls to lines out of order, or to lines on which the service has been discontinued, etc., trunks for handling these services being commonly known as intercepting trunks, and the broad object of the invention is to provide an intercepting trunking system which is more flexible, economical, and convenient in practice than anysuch system heretofore known to applicant.

A. particular object is to provide an intercepting trunking system in which, by simply removing battery potential from the cut-off relay of a line switch of a line in trouble, or an unassigned line, the calls extended there to are I automatically trunked to an intercepting operators position.

Another object is to provide means whereby an intercepting operator, upon answering a call extended to her position, is automatically informed that the number cal-led represents a called Working line which is in trouble or is a dead number, as the case may be.

Other minor features of the invention not specificaly pointed out will be brought out in the detailed description which follows.

Referring now to the drawings comprising Figs. 1 and 2, these figures, when arranged with Fig. 1 immediately above Fig. 2, show sutficient of the circuits and apparatus of an automatic telephone system to enable the invention to be clearly understood.

Referring to the figures in detail, Fig. 1 shows a connector H, line switch C, substation A, special high frequency generating equipment T, and a start relay 100. The connector H is of the well known Strowger type and is wired in accordance with the usual two-wire practice. Minor circuits additions have, however, been made in accordance with the present invention. These added circuits will be fully described hereinafter. The'line switch C is of the well known Keith or plunger type. The master switch M is of the usual solenoid type used to maintain the plungers of idle line switches before an idle trunk. The substation A comprises the usual apparatus used "in substations of automatic telephone systems. The

special high frequency generating equipment T consists of an Ordinary high frequency ibuzzer operating preferably at about 400 cycles per second. This equipment is common to any number of'lines and its purpose will be clearly brought out hereinafter. The start relay 100 is individual to the connector H, and is for apurpose which will be subsequently made clear.

Fig. 2 shows a line finder LF, trunk hunting switch TS, a finder distributer FD, a special A or intercepting operators position Y, and alsoan'operators cord circuit for answering calls extended to her position. In the cord circuitis included a very sensitive A. C. relay, which may be ofthe tyjpe disclosed'in Patent No. 1,221,299, issued to G. J. Erickson, April 3, 1917. The line finder, trunk hunting, and finder distribute! switches are mechanically the same as line switches of the well known rotary type having their wipers always in engagement with a set of bank contacts.

Having given a description of the miscellaneous equipment shown in Figs. 1 and 2,

it is deemed advisable, before going into the detailed description of the invention, to briefly describe the trunking arrangement of the intercepting system. It is assumed, in

the present case, that the connectors H are divided into groups of fiftyconnectors each.

There are provided four or five fifty point line finders LF for each group of fifty conne'ctors' and,o f course, since the trunk hunting switches are individual to their associated line finders, a like number of these switches are necessary. The trunk hunting switches may be of the twenty-five or fifty point type dependent, of course, upon the traffic conditions. For each group of conn'ectors there is provided one finder distributer FD. This finder distributer has its L wipers normally associated with an idle link llU previously operated switches in operated position in the usualmaniier.

'When the next series of impulses is transmitted over the control circuit by the calling subscriber the line relay ll'ofthe connector His momentarily deenergized a plurality of times and at each deenergization transmits animpulse of current to the vertical magnet 18 over a path which extends from ground 'by wa y of armature 24 and its resting con tact, armature 26 and its working contact, oft normal springs 21 and 23, winding of the slow acting series relay 13, and the winding of the vertical magnet 18 to battery. By the operationot the'vertical magnet the wipers -52, inclusive,,are raised stepby step untiltliey standopposite the desired level of bank contacts. Relay 13 is energized in series with the vertical magnet 18 and being slow acting holds up continuously during the vertical operation of the switch. By the operation of this relay, the vertical magnet circuit is preserved intact,notwithstanding the shifting of theott normal springs, which occurs at the first vertical step of the switch.

At the end of thevertical movement, relay 13 deenergizes and transfers the operating circuit .to the rotary magnet 19. i

i The call'ng subscriber now transmits the final series of impulsesof the called telephone number Responsive to these inter- -ruptions.the line relay 11 is deenergized a corresponding nuinber of times and now sends impulses to the rotary magnet 19 over the following circuit: from ground by way of armature 24 and its resting contact, armature and its working contact, oil normal springs 21 and 22, armature 27 and its resting contactyresting contact of armature and the said armature, armature 39 and its resting contact, and. the winding of the rotarymagnet 19 to battery. By the opera- *tion. of the rotary magnet, the wipers 50.52, inclusive, are rotated step by step and areyfinally brought to rest in engage- -ment with the particular set of bank contacts in which the line of substation A is terminated, these contacts being indicated in the drawings by reference characters .53, 54 and 55. The slow acting relay 16 is energized in parallel with the rotary magnet and remains continuously"energized during the rotary movement; In operated position, re-

-lay,16 connects the test wiper 51 to the winding of the testrelay 15 by means of its armature 33 and at armature 35. closes an alternative point in the circuit of the re tary magnet, to guard against the possibility of having this circuit opened by the operation of the test relay while the test wiper 51 is passing over grounded test contacts.

The final series of impulses lllSllOW been received, and the connector wipers have been placed in connection with the terminalsot the called line. Itth'e lincis busy there will be aground potential on the test con tact 5 L and the test relay 15 will be energized. pares a lockingcircuit for itself at its armature 31, which is completed when the slow acting relay 16 falls back aninstant later, opens the rotary magnet c rcuit at armature 32, and at armature 3-l connects a lead from the busy signaling machine to thelower side of the line. On. perceiving the signal, the subscriber will replace his receiver, thereby releasing the connector H and all previously operated switches.

Assuming now that the called line is idle when connection therewith is attempted,

under these circumstances thei'elwill be no groundon the test contact 5 1, and the test relay 15 will not be energized. Then when the slow acting relay iltii alls back a circuit is completed for the switching relay 17 which may be traced from the grounded conductor 7, by way of armature 31 and its resting contact, the upper winding of the switching relay 17,resting contact otl' ZUIIRP ture 33 and the said armature, test wiper 51, test contact 54-, contacts of the jack J, winding of the cut-oil"; or switching relay 62 of the line switch C, contacts 71 oit'c jack J 7 to battery. Relays 17 and 62 are'energized in series over this circuit, and the latter W'licn this relay operates it prc relay operates armature???)to1clcar the line conductors 60 and 61 ottheir normal battery and 3 ground connections in the line switch C. i

'At the connector H, whenwthe switching relay 17 pulls up, it establishes a locking circuit torfitselit' at armature 38, grounds the test wiper 51 at armature 37, opens the rotary magnet circuit at armature. 39, and at armatures 36 and 4:0" connects up the two line wipers 50 and 59. By the latter operation a signaling circuit ,is established whereby ringing current from the generator GEN is intermittently projected out over the called lineto operate thebridged ringer at substation A to notify the called subscriberthat he is wanted." The return path for the ringing current includes the upper :winding of the ring out off relay 1 1, and

when the called subscriber answers this relay is operated. Upon energiz1ng,'relay 1% establishes a lockingc1rciiit for itself at its armature 29, breaks the ringing circuit at armatiires 2S and 30, andat the working iri contacts of these same armatures finally completes the talking connection.

Current is now supplied to the transmitter at substantion A through the windings of the double wound back bridge relay 10 which is accordingly energized. This relay is a reversing relay and has the well known function of reversing the incoming trunk conductors 6 and 8 as regards their connections with the windings of the relay 11. This reversing operation is a standard operation and is for the purpose oi operating subscribers paystation or metering apparatus, and in some cases is used for supervlsory purposes. The subscribers may now converse as desired.

When the subscribers'are through talking they will replace their receivers, causing the connector H and all previously operated switches to be released in the usual and well known manner.

There is nothing particularly new in theoperations above described. It is thought, however, that the above description will be a material aid in making clear the various features of the invention.

It will now be assumed that the subscriber at station A has had his service discontinued,

or that the telephone at station A has been taken out. Now in order to trunk calls which may be extended to the line switch C to a special A or intercepting operators position, it is only necessary that battery potential be removed from the test contact 541 of the line switch C. This is accomplished in a simple manner by merely placing a thin piece of insulating material between springs of the jack J. Then the connector H seizes the line switch C under these "condi tions, the test wiper 51 fails to find battery, and when the slow relay 16 deenergizes, re lay 17 fails to pull up and a. circuit is completed for start relay 100. This circuit may be traced from grounded working contact of armature 49 andthe said armature, armature 81 and its resting contact, upper winding of relay 17, resting contact of armature 33 and the said armature, armature and its resting contact, armature 41 3 and its resting contact, resting contact of armature 4 1 and the said armature, rotary oft normal springs 15, conductor 46, resistance 99, and the winding of relay 100 to battery. Due to the high resistance of relay 100, switching relay 1'? does not energize, and relay 100, due to the inclusion of resistance 99, only receives sufficient current to cause it to operate its armatures 102 and 103. The operation of armature 103 causes ground to be removed from conductor 155 terminating in a bank contact of the line finder LF, at the front contact of this same armature prepares a new circuit for relay 100 independent of the resistance 99, and at armature 102 completes'a circuit for slow release relay 110 of the finder distributer. Relay 110, upon operating, at itsarmature 117 prepares locking circuits for relays 111 and 112, and at armature 116 connect-s interrupted ground to the windings of relay 111. Interrupter I is arranged to apply ground to conductor 130 for a period of one half second and then to remove ground from this conductor for a like period, As soon as ground is connected to conductor 130 relay 111, upon having a circuit completed through its upper winding, operates its armature 118, therebv short circuiting the lower winding of this relay. Armature 119 is so adjusted that it will not operate until the current flow is established through both windings of relay 111. As soon as ground is removed from conductor 130 a-circuit is completed from thegrounded working contact of armature 117 and the said armature,armature 118 and its work ing contact, and the windings of relay 111 in series to battery. Relay 111 now actuates armature 119 switching the connected conductor 130 from connection with the windings of relay 111 to the windings of relay 112. As .soon as a one half second interval has elapsed-relay 112 operates sufficiently to cause its armature 125' to engage; its working contact, and at the termination of another half second interval the short circuit is removed from the lower winding of this rely permitting it to also operate its armatures 1201241,inclusive. The operation of armature 121 completes circuits for relays 113 and 114. Thecircuit' for relay 113 may be traced from grounded working contact of armature 121 and the said'armature, winding of relay 113, wiper 131 and itsassociated contact, conductor 1 15, interrupter springs of the motor magnet156, and the winding of said magnet to battery. The circuit torrelay 11 1 may be traced from the grounded working contact of armature 121 and the.

said armature, winding of relay 1141-, conductor 108, wiper 133 and its associated con tact, conductor 136, interrupter springs of the motor magnet 139, and the winding of said magnet to battery. By the operation of armature 124 a circuit is prepared for the motor magnet 10 1 of the finder distributer F D independent of interrupter contacts129,

and by the operationoit armatures 120 and,

123 test wipers 164 and 153 are connected to junctions 105 and107, respectively.

Assuming now that the trunk hunting switch TS has its wipers associated. with a trunk line which is in use, the contact with which wiper, 164 is in engagement will have ground potential thereon and a circuit will be completed for motor magnet 156, which may be traced as follows: grounded wiper 16 1, conductor 147, armature 14:3 and itsresting contact, conductor 157, wiper 132, armature 120 and its working contact,armature 127 and its resting contact, junction 105, wiper run ers 163 -165,

131 auditsassociated contact, conductor operation of magnet 156 will be repeated.

As soon as the wiper 164 comes into engagement with the test contact associated with conductor 150 of the trunk line comprising moved from its winding,

operatin .104, and relays 115 and .156. into engagement with the bank contact with conductors 149-151, inclusive, which it is assumed is idle, no ground potential will be present on conductor 150 and theswitching relay. 113,will,no longer be short circuited andfwilltherefore operate. Since the resistance of this relay is very high compared tothat of motormagnet 156, the magnet is not operated at this time. Relay 113, upon at its armature 127 grounds he test conductor, 1500f the seized trunk, to make the same busy to other'trunk selecting switches, and at. its armature 126 prepares a point in the operating circuit of magnet .140. I i Assuming now that the wipers 152-154, inclusive, of the line finder are not in engagementwith contacts associated with connector trunk conductors 47, 48 and 155. Under these conditions ground will be present on the contact on which wiper 158 is positioned and, therefore, a circuit will be completed for motor magnet I 139, this circuit beingtraceable from the grounded test wiper153, armature 142 audits resting contact, conductor 137, wiper 134, working contact of armature 128 and the said armature, 111116131011 107 (ground at this point short circnitsrelay 114, and prevents it from operati11g),wiper. 133 and its associated contact, conductor 136,-.interrupter springs of the motor magnet 139 :and. the winding of said magnet to battery. The magnet 139 will, therefore, operate and as long as the test wiper153 comes into engagement with idle connector trunks,;will continue to operate in the same manneras explained, in

connection with the operation of magnet As soon asthe testwiper 153' comes which the ungrounded conductor 155 is as- .sociated, magnet 139 will cease to operate and relay 114, havlng the bflOlt.Cl1C111t 1ewill now energize. Since both switching relays 113 and 114 are now operated multiple circuits are completed for motor magnet 104 and relays 115 and 140, respectiyely. The circuit for magnet 104 may be tracedv from grounded working contact of armature 1261 and the saidv armature, armature 128- and its working contact, through thewlnding of motorfmag reea rre net 104tobattcry. flhc circuits ofrelays 115 and 140. extendby way of armature 128 and its working contact-,ovorkingcontact 0t armatureyl24, to junction 17 5 where the cir-. cult divides, one branch extending direct to.

the winding of relay .115 and. to battery,

while the other branch extendsb-y way of.

104. and relay 1151 wiper 153 from engagement with conductor 7 137 and connects this wiper to" grounded conductor 138. The line relay 11 of the connector H is bridged across conductors 6 and 8,, which are now extended by way of conductors 47 and 48,:eonductors 146 and .148 toconductors 149 and 1 51.a1cr0ss.' which are bridged the windings of relay 172 at the intercepting operators position. Relay 17 2 in multiple with line relay 11 andoperates at its armature 167 connects interrupted generator tothe conductor 149 by, Wayfot armature 173 and its resting contact and low capacity condenser168. Condenser 168 allows just sufficient current to leak back over the calling line to give the calling subscriber the usual ring-back tone tointorni him that the signaling operation. is taking place Relay 172 also, at armature. 1610, completes a circuit for the call signal lamp L, which glows to notify the intercepting operator that a call is awaiting her attenductor 150 to maintain the trunk busy to other trunk selecting switches independent of ground supplied by way of Wiper 135, and to provide a holding circuit for relays 140 and after the finder distributor has stepped ahead.

At the sametn'ne that the circuit tor reground to be removed from the common start conductor, while armature 181 short circuits high resistance 99.: The latter operation continues the holding circuit groundon conductor 150' back to the test wiperof the conne'ctor, thus shunting the upper winding of relay 17 so that it another connector, should connect with the same line relay 17 wouldg tion, and at armature v159 applies ground through a low resistance retard 0011 to con lay 172. was completed, .a new circuit was not pull in series with the, busy test relay of the second connector. Y

It will be recalled that slow release relay 115 and motor magnet- 104 were energized in multiple with switchingrelay 1 10. The result of theop-eration of relay 115 and magnet 10% will now be described. Relay 115 operates and opens the circuit of relay 110. Relay 110, upondeenergizing, at its armature 117 opens the locking circuits of relays 111 and 112. These relays, accordingly, deenergize. The deenergization of relay 111 in no way affects the operation of finder distributor FD. Relay 112, however, upon deenergizing, at its armature 121 breaks the circuits of switching relays 113 and 11st and these relays, accordingly, restore to normal. The deenergization of relays 113 and 114: causes ground to be removed from the common operating circuit.

of relays 115, 140 and motor magnet 104-. Magnet 104 and relay 115, accordingly, deenergize. Relay 140, however, does not deenergize due to the previously described holding circuit completed for it by the op eration of armature 159 of relay 172. Magnet 104, upon deenergizing, shifts its wipers 131136, inclusive, into engagement with the next link circuit. If the next link circuit happens to be in use at this time its associated conductor138 will have ground potential thereon and an operating circuit for magnet 104 will again be completed by way of wiper 135, interrupter contacts 129, and the winding of said magnet 104 to battery. Upon the complete energization of magnet 104 the interrupter springs 129 are opened, and this magnet, therefore, deenergizes to advance the wipers into engagement with the next link. It will be quite evident that this operation will be repeated until an idle link circuit is found. Since relay 115 is connected to wiper 135 this relay receives ground impulses in multiple with magnet 104 and, being slow to release, will remain operated during the operation of magnet 104 to maintain the relay 110 disconnected from the common start con- (luctor until an idle finder link is found.

Assuming now that no other connector, of the group to which connector H belongs, has in the meantime been positioned on contacts of a line introuble, etc., no other start relay, such as 100, will be operated, and since, as previously explained, armature 101 of relay 100 is now operated no ground is present on conductor 175 and relay 110, therefore, does not again operate. If, however, it be assumed that a connector has in the meantime been positioned on contacts of a line in trouble, etc., its associated relay 100 will be energized and therefore .conductor 175 will have ground potential thereon and relay 1.10 will again operate to initiate the operation of the preselected finder link in the same manner as scribed. i

, The operations which take place at the intercepting operators position will now be described. The intercepting operator, upon observing the lighted condition of lamp L inserts the plug P of her cord circuit in the ackJ, thereby closing acircuit for relay 17 1. Belay 174, upon operating, removes ground from conductor 150 and completes 76 a, circuit for relay 158. Relay 158, upon operating, at its lower armature opens the circuit of lamp L, and locks itself up through its upper winding and the working contactof this same armature, and at its armature 173 disconnects interruptedgenerator tone from the upper line conductor. When the plug was inserted in j ack J sleeve relay 170. in the cord 0 energized in series with relay 14:0. Relay 170 in operating com-. pleted a circuit for slow relay 171. This latterrelay in operating prevented the lamp L from being lighted. Since the lamp L fails to, glow the operator knows that the call has been. extended to a dead number. The sleeve of the plug applies ground to the sleeve of the jack J via low resistance relay 170 in substitution of the groundformerly supplied by way .of the operated armature 159 to maintain the trunk ,Y busy to other trunk selecting switches. a The operator may now operate key K and converse ,with the calling subscriber,

giving such subscriber anyinformation she may have available regarding the number 100 of the desired called subscriber. WVhen the conversation is completed the calling subscriber replaces his receiver, resulting in the release of the connector H and all previously operated switches. Since relay 172 is 105 connected in multiple with relay .11, relay 172 also restores and in so doing opens the previously delocking circuit of relay 158. During the restorlng operation of connector H off normal springs 45 openthe holding circuit, and asa result these relays restore to normal. Since ground is now removed from the conductor 138, the finder link, comprising switches LF and TS is again rendered selectable by the wiper 135 of the finder distributer FD.

The operator upon removing the plug from the associated jack causes relays 17 1 and 158 to deenergize. Ground being now removed from conductor 150 the trunk is me again rendered selectable.

It will now be assumed that the line switch C is assigned to the line extending to substation A, and that this line is temporarily in trouble. Under these conditions, the attendant at the exchange will insert a plug P of the common apparatus T between springs 70 of jack J, thereby substituting ahigh frequency current to the upper one of the springs 70 for the battery formerly i supplied via springs 71 and winding 62 of the line switch G. Upon a connection being attempted with'the working line A in When the operator plugs into jack J, acircuit is completed for A, C. relay 162. This circuit may be traced from high frequency apparatus T, plug P upper one of the sarin s 70 bank contact 54 W13G1 51 armature 37 and itsresti'ng contact, armature 43 and its "restingcontact, resting contact of armature 1 1 and the saidarmature, rotary off normal contact 45, conductor 46, armature 181 and its working contact, working contact of armature 103 and the said armature, conductor 155, wiper 153, armature 1 12 and itsworking contact, working contact oi armature 143 and the said armature, conductor 14:7,wi'per 164,0onductor 150, sleeve of jack J, sleeve side of plug P, condenser 163, and the winding of relay 162 to ground. Relayf162 thereforeoperates at the same time as does relay 170, therebypreventing the operation of relay 171. Lamp Lis therefore lightedto immediately inform the operator of the character ofthe called line thereby enabling-the operator to convey such information to the calling subscriber without delay.

After conversation has been completed, release isbrought about in the same manner as previously described;

Before concluding, it isthought advisable to explain the reason for providing the equipment comprising interrupter I and twostep relays 111 and .112 for delaying the operation of the switches LF and TS. It will benotedthat a connector, such as H, upon switching through, transmits a momentary ground impulse to its associated start relay 100 over a circuit extending from grounded conductor 7 armature 31 and its resting contact, upper winding of relay 17, resting contact of armature 382111Cl the said armature, armature 37 and its resting contact, over the previously traced "CllClllll through the associated start relay. The possibility of a number of connectors, switching through in close sequence, resulting in the starting of a finder link is made impossible by the use of thisdelaying inechaii'isn'i.

Attention is also called to the fact that since the holdingcircuit used for the transmission of the high frequency currents-to the operatoris nowhere connecteddirect to ground or battery, evenbefore the operator plugs in to answer the call,'it is possiblefor the operator to, test for the presence of these signalling currents on the sleeve of the jack before plugging in, thesaine asEwhen testing a line to see if it is busy. WVhen this method of operationis followed thespecial equipment shown in the-cord circuit 0 is 01' course not needed and astandard subscribers operators cord circuitimay be used.

Having fully described the invention,

what is considered new and is desired to have protected by Letters Patent will be pointed out in. the appended claims.

Vhat I claim is:

1. In a telephone system,a calling line,

called lines, unassigned called lines, other called lines assigned but temporarily out of service, means including automatic switches for extendinga connection to, any of said called lines, means responsive" when a connection is extended to either of the latter type of called lines forautomatically t-run'kiiig the call to an operators switchboard,

and means wherebyan operator upon answering is immediately informed of the class oflinecalled. i

2. In a telephone system, unassigned called lines, other called lines assigned. but temporarily outer service,

means including automaticswitches for eX-' tending connections to said called "lines, means responsive whena connection is extended to either of the above type of called lines for automatically trunking thecallto.

an operators switchboard, a visual signal at said switchboard, means operative when an operator answers a call for causing the operation of said signal if the line called is ofthe latter type, and means operativepreventing theoperation of saidsignalin case the called line is of the first type.

3. In atelephone-system,a called line temporarily out of service, a, connector switch adapted tobe coutrolledover a calling line'to connectwith said called line,an operators switchboard, a link circuit comprising a finder switch andahunting switch, and a start relay associated with said. connector operative when said line is called for causing said link circuit toconnectthe calling line with saidswitchboard.

1. In a telephone system, a connector switch, wipers for said switch adapted to be positioned on terminals of "-alled lines, a switching relay in said connector operative when a lineis called. means torpreventing a calling line,

ii-s

the operation of'saidrelay should the line i called be in trouble, and means operative should the switching relay fail to operate within a predetermined period for causing said connection to be extended to an operators switchboard; i

5; Ina telephone system, called lines oi. different classes, an automatic switch having access to said lines. subscriber controlled means for causingsaid automatic switch to extend connections to said lines as desired, an operators switchboard, means for automatically trunking calls extended to a calling line,

certain of said called lines to said switchboard, a visual signal at said switchboard, means, thereat operated when the operator answers the call if the called line is of one class for causing the operation of said signal, and means operated iii the called line is of a different class for preventing the operation of said signal.

6. In a telephone system, an automatic switch, subscriber controlled means for controlling the operation of said switch, to ex-' tend connections to called lines of different classes, an operators switchboard, means for trunking connections extending to called lines of certain classes to said opera-tors switchboard, a call signal-at said switchboard operated when a. connection is extend cd thereto, a cord circuit, and means associated with said cord operated or not operated dependent on the particular class-of line called. when the operator answers the call to inform such operator of the particular class of the called line.

7. In a telephone system, a calling subscribers line normally having direct access via automatic switches. to other subscribers lines, means for temporarily plugging any line out of service, an operatorsswitchboard having a plurality of. trunks terminating therein, a trunk hunting switch, a line finder switch, a finder distributer switch, circuit arrangements for causing said finder distributer switch to operate responsive to any call ing line extending a connection to a called line out of service, and means in said distributer for controlling said trunk hunting switch to. find an idle switchboard trunk and said line finder switch to find the extended calling line and connect it to said idle switchboard trunk.

8. In a telephone system, a calling line, a connector switch, a called line terminating in a. line switch, a plug ending tone machine for plugging out said line switch, subscriber controlled means for causing said connector switch to extend said calling line to said called line, an operators switchboard, means responsive to the attempted extension of said calling line to said called line if the line switch has been plugged out, for trunking said calling line to said switchboard, a plug ending cord circuit including a signal, and means in said cord circuit responsive to said tone machine for controlling the operation of said signal when the operator plugs into said trunked line to inform ,her of the particular class of the called line.

9. In a telephone system, an automatic switch, subscriber controlled means for controlling the operation of said switch to extend connections to called lines of different classes, a plug ending tone machine for plugging out lines of one class, an operators switchboard, means responsive to the extension of a calling line to a plugged-out line cuit for trunking said calling line to said operators switchboard, a call signal at said switchboard operated when a connection is extended thereto, and a cord circuit for testing for the presence of said tone machine and answering said call. 10. In a telephone system, a line having a test contact, a source of signalling current connected to said contact, means including an automatic switch for extending a connection to-said line, said switch having a test wiper for engaging said test Contact, a jack ending trunln means including another automatic switch for extending a. branch of said connection to said trunk, anda signalling cirextending from said test contact through all said switches to the sleeve of said jack. 1 Y I 11,. In a. telephone; system, a line having a, test contact, a source of signalling current connected to said contact, means including an automatic switch for extending a con nection tovsaid line, said switch having'a test wiper for engaging said test contact, a'

trunk line extending to an operators switchiioard, means including another automatic switch for extending a branch of said connection to said trunk, a non-talking conductor extending from said test contact through both; said switches to said switchboard, and a signalling circuit including said conductor.

12, A telephone system as set forth in claim 11 in which the said second switchincludes a relay energized over said conductor for maintaining the connection.

13', In a telephone system, lines to which service is denied and lines to which service is given, both accessible by way of an automatic switch, means for operating the switch to extend a call to either class of lines, means responsive to the calling of a line of the first mentioned class for extending the call to an operators switchboard, the lines of the first mentioned class consisting of two subclasses of lines, and means for automatically indicating to the operator the particular subclass of' the called line. i

14. In a telephone system, a line including talking conductors and a test conductor, means for establishing a connection to the line, means for testing thebusy or idle condition of the line, means effective if the line is idle for completing the connection, and means effective in the event the line is idle and the last named means fails to operate and directly controlled by said last named means, for extending the call to an operators switchboard.

15. In a telephone system, a connector switch for extending a connection to a called line, a switching relay in the connector operative to complete a link in the connection if the line is idle, means effective underpredetermined idle conditions of the line for preventing the operationof the relay, andlneans effective in response to the failure of said relay to operate for causing the calling connection to'be extended to an operators switchboard.

16. In a telephone system, a line inclnding a test condnctor, means for establishing a connection to the line, a plurality oftrunks extending to an operators switchboard, andtiine delayed means effective if the test condnctor is open to seize any idle trunk in said group of trunks and extend the call thereover. i i

17. In a telephone system, aline including a test conductor, means for establishing a connection to the line, a plurality of trunks extending to an operators switchboard, time delayed means for extending the call to any idle trunk in said group of trunks, and means controlled over the test conductor for rendering said last named means ineffective.

18. In a telephone system, a line including a test conductor, means for extendingja call 1 to the line, a trunk terminating at an operators switchboard, nieansinclnding a finder effective when operated to extend the call over the trunk, tin e delayedmeans for starting the finder to operate, and means controlled over thetest conductor for rendering the second nainedineans ineffective.

19. In a telephone system, a trunk extend- I ing to a connector switch, a branch of the trunk accessible to a finder switch, a starting relay for the finder switch, a test relay and a switching relay in the connector, circuit connections for the starting relay established when the connector has been operated if the test relay and the switching relay are not operated, and means ing relay for starting thefinder switch to hunt for the branch of the trunk.

20. "In a telephone system, a trunk extend controlled by the starting to a connector switch, a branch of the V for extending a connection from said branch by way of the finder switch to an operators headset. i i v 21'. In a telephone system, a trunk, a connector including a test ngrelay and a switching relay, a plurality of lines accessible'to the connector, means for operating the connector over thetrunk to select a desired line, a finder switch, a branch of the trunk tenninating in the bank of said finder switch, means including a starting relay effective if the test relay and the switching relay both tail to operate for starting the finder tohunt for the branch of the trunk, and means for extending a connection from the branch by way of the finder switchto an operators headset. 1 i i i In witness whereof, I hereunto subscribe my name this 31st day of January, A. D. 1924. v i

a MICHAEL SCHWARTZ. 

